Study On Sludge Dewatering By Coupling Process Of Electro-osmosis Biodring

The water content of sludge is still higher than 80%after mechanical dewatering which is difficult to transport and final disposal.Sludge dewatering is a necessary process for sludge disposal.How to ensure further sludge dewatering with high efficiency and low cost has become a key breakthrough of sludge disposal and treatment.In this paper,we used the sludge after mechanical dewatering for the research and combined the respective advantages of the electro-dewatering technology and biological drying technology,to establish the combined process of“electro osmosis-biodring”:which made sludge be dewatered quickly to the moisture content of 60-70%by electro-dewatering technology at high moisture contents;then the electro osmosis dewatering sludge was dried by biodring technology with low cost,the combined process could reduce cost and improve the drying efficiency with dual value of basic theory and practical application.For the process of residual sludge electro osmosis dehydration in combined process,voltage gradient,the thickness of the filter cloth,electro osmotic time,these operating parameters were optimized,and the change of sludge's characteristics on the performance of electro-dewatering was also discussed in this paper.From the perspective of dewatering efficiency and energy conservation,the optimal operating conditions for the electro-dewatering of sewage sludge were determined to be the voltage gradient of 20 V/cm,medium thin filter cloth,the electro osmotic time of 9min,under the optimum operating condition,the energy consumption when the moisture content of the dewatered sludge was 65%was 0.13-0.18 kWh/(kg removed water).During the electro-osmotic dewatering of sludge,water was electrolyzed in the area of electrodes so that H~+would generate near the anode and OH~-would generate near the cathode.Because of the action of the electro-migration,the positively charged substances could move to the cathode and the negatively charged substances could move to the anode.Therefore,after the electro-osmotic dewatering,the moisture content,volatile substances content,pH,conductivity would have some changes.For the process of biodrying of electro osmosis dewatering sludge in combined process,product reflux,ventilation rate,turning frequency,initial moisture content,these operating parameters were optimized,and the results of the control study of natural drying sludge and electro osmotic dewatering sludge were demonstrated,the effects of the particle size,type and the proportion of the bulking agent were discussed to study the effects of porosity and carbon source on the temperature and moisture content of the reactor.The optimal parameter control conditions for sludge biodrying were:ventilation rate 0.08 m~3/(h·kg),aeration frequency 3 min O/7 min S,6 days experiment period,2 days turning frequency,65%initial moisture content,straw as bulking agent,m sludge:m straw=5:1,m sludge:m reflux=3:1.The matter and energy balance calculations of the biodrying system found that,the moisture removal rate of43.10%and organic matter consumption rate of 15.65%,the energy utilization efficiency of 6.15 kg water/kg VS.Each part of the heat dissipation rate is very different in reactor with different sizes,small reactor itself lost too much heat made the sludge moisture content decline is limited.Taking into account the basic cost,“electro osmosis-biodring”combined process is a technology that is worth popularizing which combination is good,the equipment operating efficiency is high,the cost is low and the occupancy area is small.